Systems and methods for mobile phone location with digital distributed antenna systems

ABSTRACT

Methods and systems for mobile phone location within a digital distributed antenna system (DAS) are provided. In one embodiment, a method comprises: receiving a request for location services from a subscriber unit located within a digital DAS, the digital DAS including a first partition of bandwidth for transporting digitized RF signals of one or more modulated signals and a second partition of bandwidth for an Ethernet pipe transporting IP formatted data; routing the request for location services to a subscriber locator center; instructing locator receivers within a geographical area of the digital DAS to listen for a signal from the subscriber unit; listening for the signal at a first locator receiver; when the signal is observed, recording a time the signal was received and generating subscriber unit ranging data; and transmitting subscriber unit ranging data back to the subscriber locator center in an IP formatted message via the Ethernet pipe.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/144,257, filed on Jan. 13, 2009, which is incorporated herein byreference in its entirety.

This application is related to U.S. Provisional Application No.61/144,255 filed on Jan. 13, 2009 entitled “SYSTEMS AND METHODS FOR IPCOMMUNICATION OVER A DISTRIBUTED ANTENNA SYSTEM TRANSPORT”, and which isincorporated herein by reference in its entirety.

This application is related to U.S. patent application Ser. No.12/555,912, filed on Sep. 9, 2009, entitled “SYSTEMS AND METHODS FOR IPCOMMUNICATION OVER A DISTRIBUTED ANTENNA SYSTEM TRANSPORT”, and which isincorporated herein by reference in its entirety.

BACKGROUND

A Distributed Antenna System, or DAS, is a network of spatiallyseparated antenna nodes connected to a common node via a transportmedium that provides wireless service within a geographic area orstructure. Common wireless communication system configurations employ ahost unit as the common node, which is located at a centralized location(for example, at a facility that is controlled by a wireless serviceprovider). The antenna nodes and related broadcasting and receivingequipment, located at a location that is remote from the host unit (forexample, at a facility or site that is not controlled by the wirelessservice provider), are also referred to as “remote units.” Radiofrequency (RF) signals are communicated between the host unit and one ormore remote units. In such a DAS, the host unit is typicallycommunicatively coupled to one or more base stations (for example, viawired connection or via wireless connection) which allow bidirectionalcommunications between wireless subscriber units within the DAS servicearea and communication networks such as, but not limited to, cellularphone networks, the public switch telephone network (PSTN) and theInternet.

A problem arises with implementing emergency (e.g. 911) responsessystems for wireless communication systems however, because unlike landbased telephones which are each associated with a physical address, thephone number of a mobile phone calling in to report an emergency doesnot convey the location from which the call originates. While wirelesslocation algorithms and systems exits, and distributed antenna systemsexist, using wireless location algorithms within an area serviced by adistributed antenna system results in location ambiguity due to multipleantenna sites.

For the reasons stated above and for other reasons stated below whichwill become apparent to those skilled in the art upon reading andunderstanding the specification, there is a need in the art for systemsand methods for wireless location systems within a distributed antennasystem.

DRAWINGS

Embodiments of the present invention can be more easily understood andfurther advantages and uses thereof more readily apparent, whenconsidered in view of the description of the preferred embodiments andthe following figures in which:

FIG. 1 is a block diagram of a distributed antenna system (DAS) of oneembodiment of the present invention;

FIG. 2 is a block diagram of a remote unit of one embodiment of thepresent invention;

FIG. 3 is a flow chart of a method of one embodiment of the presentinvention;

FIG. 4A is a block diagram of a remote unit of one embodiment of thepresent invention;

FIG. 4B is a block diagram of a remote unit of one embodiment of thepresent invention; and

FIG. 5 is a block diagram of a host unit of one embodiment of thepresent invention.

In accordance with common practice, the various described features arenot drawn to scale but are drawn to emphasize features relevant to thepresent invention. Reference characters denote like elements throughoutfigures and text.

SUMMARY OF THE CLAIMS

Methods and systems for mobile phone location within a digitaldistributed antenna system (DAS) are provided. In one embodiment, amethod for gathering location data within a digital distributed antennasystem comprises: receiving a request for location services from asubscriber unit located within a digital distributed antenna system, thedigital distributed antenna system including a first partition ofbandwidth for transporting digitized radio frequency (RF) signals of oneor more modulated signals, the digital distributed antenna systemfurther including a second partition of bandwidth for an Ethernet pipefor transporting Internet Protocol (IP) formatted data; routing therequest for location services to a subscriber locator center;instructing a plurality of locator receivers within a geographical areaof the digital distributed antenna system to listen for a signal fromthe subscriber unit; listening for the signal from the subscriber unitat a first locator receiver of the plurality of locator receivers; whenthe signal is observed by the first locator receiver, recording a timethe signal was received and generating subscriber unit ranging data; andtransmitting subscriber unit ranging data back to the subscriber locatorcenter in an IP formatted message via the Ethernet pipe provided by thedigital distributed antenna system.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings that form a part hereof, and in which is shown byway of specific illustrative embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that other embodiments may be utilized and that logical,mechanical and electrical changes may be made without departing from thescope of the present invention. The following detailed description is,therefore, not to be taken in a limiting sense.

FIG. 1 is a block diagram of a distributed antenna system (DAS) 100 ofone embodiment of the present invention. DAS 100 includes a host unit102 and a plurality of remote units 106. At the physical layer, hostunits 102 and remote units 106 are interconnected via fiber optic cableas indicated in FIG. 1 to form a bidirectional communication linknetwork comprising a plurality of point-to-point communication linksshown at 130. Optionally, host units 102 and remote units 106 may beinterconnected via coaxial cable, or a combination of both coaxial cableand fiber optic cable. Remote units 106 each house electronic devicesand systems used for wirelessly transmitting and receiving modulatedradio frequency (RF) communications via antenna 107 with one or moremobile subscriber units 108. Host unit 102 is coupled to at least onebase transceiver station (BTS) 110 often referred to as a base station.BTS 110 communicates voice and other data signals between the respectivehost unit 102 and a larger communication network via a gateway 124coupled to a telephone system network 122 (for example, the publicswitched telephone network and/or wireless service provider networks)and an internet protocol (IP) network 124, such as the Internet. In oneembodiment, DAS 100 comprises part of a cellular telephone network andsubscriber units 108 are cellular telephones.

Downlink RF signals are received from the BTS 110 at the host unit 102,which the host unit 102 uses to generate one or more downlink transportsignals for transmitting to one or more of the remote units 106. Eachsuch remote unit 106 receives at least one downlink transport signal andreconstructs the downlink RF signals from the downlink transport signaland causes the reconstructed downlink RF signals to be radiated from aremote antenna 107 coupled to or included in that remote unit 106. Asimilar process is performed in the uplink direction. Uplink RF signalsreceived at one or more remote units 106 from subscriber 108 are used togenerate respective uplink transport signals that are transmitted fromthe respective remote units 106 to the host unit 102. The host unit 102receives and combines the uplink transport signals transmitted from themultiple remote units 106. The host unit 102 communicates the combineduplink RF signals to the BTS 110 over a broadband medium.

DAS 100 comprises a digital DAS transport meaning that the downlink anduplink transport signals transmitted between host unit 102 and remoteunits 106 over communication links 130 are generated by digitizing thedownlink and uplink RF signals, respectively. In other words, thedownlink and uplink transport signals are not analog RF signals butinstead are digital data signals representing digital RF samples of amodulated RF signal. For example, if a particular communication signaldestined for transmission to subscriber unit 108 is a modulated RFsignal in the 900 MHz band, then host unit 102 will generate basebanddigital samples of the modulated 900 MHz RF signal from BTS 110, whichare then distributed by host unit 102 to the remote units 106.Alternatively, an all-digital BTS may generate baseband digital samplesdirectly. At the remote units, the digital samples of the modulated RFsignal are converted from digital into an analog RF signal to bewirelessly radiated from the antennas 107. In the uplink analog RFsignals received at remote unit 106 are sampled to generate RF datasamples for the uplink transport signals. BTS 110, host unit 102 andremote units 106 each accommodate processing communication signals formultiple bands and multiple modulate schemes simultaneously.

It is understood in the art that RF signals are often transported atintermediate frequencies (IF) or baseband. Therefore, within the contextof this application, the terms “digital RF”, “digital RF signal”,“digital RF samples” and “digitized RF signals” are understood toinclude signals converted to IF and baseband frequencies.

In addition to communicating the downlink and uplink transport RFsignals, the digital transport between host unit 102 and each remoteunits 106 includes sufficient bandwidth (that is, in excess of what isnecessary to transport the digitized RF data samples) to implement anEthernet pipe between each remote unit 106 and the host unit 102 forcommunicating subscriber unit ranging data to a subscriber locatorcenter (SLC) 140 in communication with host unit 102 via BTS 110. In oneembodiment, the Ethernet pipe provides a bandwidth of at least 100Mbits/sec. By taking advantage of the distributed antenna locationswithin DAS 100, SLC 140 can collect subscriber unit ranging data frommultiple locations within an area and determine the exact location of asubscriber unit for e911 emergency services or other applications. Inone embodiment, SLC 140 pinpoints the subscriber unit usingmultilateration, also known as hyperbolic positioning, wherein asubscriber unit can be accurately located by computing the timedifference of arrival (TDOA) of signals received by multiple remoteunits 106. That is, when an RF signal is transmitted by subscriber unit108, that RF signal will reach different antennas 107 within DAS 100 atdifferent times, depending on the range between the subscriber unit 106and the antennas. The TDOA is the difference in time between the RFsignal being received at a first antenna and the RF signal beingreceived at a second antenna. Given the a priori known location of twoantennas, and a TDOA measurement between the two antennas, the locationof the subscriber unit 108 can be placed onto the surface of ahyperboloid. Additional TDOA measurements from additional antennalocations allows the location of the subscriber unit 108 to be furthernarrowed down based on the intersection of multiple hyperboloids.Typically, two TDOA measurements between three antennas is sufficient tolocate a subscriber unit, although additional TDOA measurements andantennas will increase the accuracy of the calculation.

FIG. 2 is a block diagram of a remote unit 200 of one embodiment of thepresent invention such as the remote units 106 discussed with respect toFIG. 1. Remote unit 200 includes a serial radio frequency (SeRF) module220, a digital to analog radio frequency transceiver (DART) module 208,a remote DART interface board (RDI) 224, a linear power amplifier 210,antenna 212, a duplexer 211, a low noise amplifier 214 and a locatorreceiver (LR) 216. In one embodiment, SeRF modules and DART modules andlocator receivers described herein are realized using FPGAs, ASICs,digital signal processing (DSP) boards, or similar devices.

DART module 208 provides bi-directional conversion between analog RFsignals and digital sampled RF for the downlink and uplink transportsignals transmitted between host unit 102 and remote units 106. In theuplink, DART module 208 receives an incoming analog RF signal fromsubscriber unit 108 and samples the analog RF signal to generate adigital data signal for use by SeRF module 220. Antenna 212 receives thewireless RF signal from subscriber 108 which passes the RF signal toDART module 208 via low noise amplifier 214.

In the downlink direction DART module 208 receives digital sampled RFdata from SeRF module 220, up converts the sampled RF data to abroadcast frequency, and converts the digital RF samples to analog RFfor wireless transmission. After a signal is converted to an analog RFsignal by DART module 208, the analog RF signal is sent to linear poweramplifier 210 for broadcast via antenna 212. Linear power amplifier 210amplifies the RF signal received from DART module 208 for output throughduplexer 211 to antenna 212. Duplexer 211 provides duplexing of thesignal which is necessary to connect transmit and receive signals to acommon antenna 212. In one embodiment, low noise amplifier 214 isintegrated into duplexer 211.

DART modules in a remote unit are specific for a particular frequencyband. A single DART module operates over a defined band regardless ofthe modulation technology being used. Thus frequency band adjustments ina remote unit can be made by replacing a DART module covering onefrequency band with a DART module covering a different frequency band.For example, DART module 208 is designed to transmit 850 MHz cellulartransmissions. As another example, DART module 208 transmits 1900 MHzPCS signals. Some of the other options for DART modules 208 includeNextel 800 band, Nextel 900 band, PCS full band, PCS half band, BRS,WiMax, Long Term Evolution (LTE), and the European GSM 900, GSM 1800,and UMTS 2100. By allowing different varieties of DART modules 208 to beplugged into RDI 214, remote unit 102 is configurable to any of theabove frequency bands and technologies as well as any new technologiesor frequency bands that are developed. Also, a single remote unit may beconfigured to operate over multiple bands by possessing multiple DARTmodules. The present discussion applies to such multiple band remoteunits, even though the present examples focuses on a the operation of asingle DART module for simplicity.

SeRF module 220 is coupled to RDI 224. RDI 224 has a plurality ofconnectors each of which is configured to receive a pluggable DARTmodule 208 and connect DART module 208 to SeRF module 220. RDI 204 is acommon interface that is configured to allow communication between SeRFmodule 220 and different varieties of DART modules 208. In thisembodiment, RDI 204 is a passive host backplane to which SeRF module 220also connects. In another embodiment, instead of being a host backplane,RDI 204 is integrated with SeRF module 220. When a remote unit operatesover multiple bands by possessing multiple DART modules, RDI 204provides separate connection interfaces allowing each DART module tocommunicate RF data samples with SeRF module 220. Although FIG. 2illustrates a single SeRF module connected to a single RDI, embodimentsof the present invention are not limited to such. In alternateembodiments, a SeRF module may connect to multiple RDIs, each of whichcan connect to multiple DARTS. For example, in one embodiment, a SeRFmodule can connect to up to 3 RDIs, each of which can connect to up to 2DARTs.

SeRF module 220 provides bidirectional conversion between a serialstream of RF, IF or baseband data samples (a SeRF stream) and a highspeed optical serial data stream. In the uplink direction, SeRF module220 receives an incoming SeRF stream from DART modules 208 and sends aserial optical data stream over communication links 130 to host unit102. In the downlink direction, SeRF module 220 receives an opticalserial data stream from host unit 102 and provides a SeRF stream to DARTmodules 208.

Remote unit 200 further includes a location receiver (LR) 216 forgenerating subscriber unit ranging data used in determining the locationof a subscriber unit transmitting to remote unit 200. In the embodimentshown in FIG. 2, LR 216 receives an analog signal feed of the RF signalsreceived at remote unit 200 via antenna 212. In one embodiment, lownoise amplifier 214 includes a secondary RF tap from which LR 216receives the analog signal feed of the RF signals. LR 216 is alsocoupled to SeRF module 220 via an interface 222 that providesbidirectional access to the Ethernet pipe between remote unit 200 andthe host unit 102. In one embodiment, interface 222 is a receptacle fora standard 8 Position 8 Contact (8P8C) modular plug and category 5/5ecable. In operation, LR 216 evaluates the RF signals received at antenna212, looking for a signal from a particular subscriber unit, such as anindividual's cellular phone for example. For example, in one embodiment,LR 216 evaluates the RF signal of a particular communication channel tomake a timing measurement for a particular subscriber unit. When LR 216finds the signal it is looking for, LR 216 generates a messageindicating the time at which the signal was received at that remoteunit. This message is referred to herein as subscriber unit rangingdata. LR 216 formats the subscriber unit ranging data for transmissionover an internet protocol (IP) network. LR 216 then outputs thesubscriber unit ranging data to the SeRF module 220 which in turn routesthe subscriber unit ranging data over the Ethernet pipe for transport toa subscriber locator center such as SLC 140. The digital distributedantenna system as described above thus includes a first partition ofbandwidth for transporting digitized radio frequency (RF) signals and asecond partition of bandwidth implementing an Ethernet pipe fortransporting the subscriber unit ranging data as IP formatted data. Inone embodiment LR 216 comprises a “Location Measurement Unit”, or “LMU”,device produced by TruePosition, Inc. and the subscriber locator center140 comprises a Gateway Mobile Location Center produced by TruePosition,Inc.

Although FIG. 2 (discussed above), and FIGS. 4A and 4B (discussed below)each illustrates a single DART module coupled to a SeRF module, a singleremote unit housing may operate over multiple bands and thus includemultiple DART modules. In one such embodiment, the systems illustratedin FIGS. 2, 4A and 4B would simply be replicated once for each band. Inone alternate embodiment, a SeRF module also allows multiple DARTmodules to operate in parallel to communicate high speed optical serialdata streams over a communication link with the host unit. In one suchembodiment a SeRF module actively multiplexes the signals from multipleDART modules (each DART module processing a different RF band) such thatthey are sent simultaneously over a single transport communication link.In one embodiment a SeRF module presents a clock signal to each DARTmodule to which it is coupled to ensure synchronization.

FIG. 3 is a flow chart illustrating a method of one embodiment of thepresent invention. The method begins at 310 with receiving a request forlocation services when a subscriber unit, such as a mobile phone,requests location services from within a digital DAS. In one embodiment,the request for location services could comprise an emergency 911 callfor help. In other embodiments, the request for location services wouldaid one or more other applications running on the mobile phone, such as,but not limited to, an application for finding nearby businesses. Thelocation services request is received as a wireless analog RFtransmission by at least one remote unit antenna of a distributedantenna system having a digital transport. That is, the downlink anduplink transport signals transmitted between the DAS host unit and theremote units are generated by digitizing the downlink and uplink RFsignals, respectively. The method proceeds to 315 where the locationservices request is routed using standard call services to a subscriberlocator center.

The method proceeds to 320 where the subscriber locator center instructsLRs located at remote units within a geographical area to listen for asignal from the requesting mobile phone. In one embodiment, theinstructions to the LRs are routed to the LRs through an Ethernet pipeprovided within the digital transport of the DAS. The method proceeds to330 where the LRs listen for the signal from the requesting mobilephone. For example, in one embodiment, the LR scans the RF signal toidentify an emergency 911 call from a subscriber unit. When the LRsreceive the signal (determined at 340), they record the time the signalwas received (350) to generate subscriber unit ranging data and sendsubscriber unit ranging data back to the subscriber locator center (360)by transmitting an IP formatted message over the Ethernet pipe providedwithin the digital transport of the DAS. In one embodiment, when thesubscriber locator center receives subscriber unit ranging data from asufficient number of LRs (typically three or more), the subscriberlocator center determines the location of the mobile phone based onsignal reception time data provided in the subscriber unit ranging data.In one embodiment, the subscriber locator center applies multilaterationalgorithms which compute the time difference of arrival (TDOA) ofsignals received by LRs at multiple remote units in order to determine aposition estimate of the mobile phone. The position estimate may then becommunicated to emergency authorities, or back to the mobile phone.

FIG. 4A is an alternate embodiment of a remote unit 400 of oneembodiment of the present invention such as the remote units 106discussed with respect to FIG. 1. Remote unit 400 includes a serialradio frequency (SeRF) module 420, a digital to analog radio frequencytransceiver (DART) module 408, a RDI 424, a linear power amplifier 410,a duplexer 411, antenna 412, a low noise amplifier 414, each of whichoperate as discussed above with respect to FIG. 2. In one embodiment,low noise amplifier 414 is integrated into duplexer 411.

Remote unit 400 further includes a location receiver (LR) 416 forgenerating subscriber unit ranging data used in determining the locationof a subscriber unit transmitting to remote unit 400. SeRF module 420 iscoupled to a RDI 424. RDI 424 has a plurality of connectors each ofwhich is configured to receive a pluggable DART module 408 and connectDART module 408 to SeRF module 420 as described above in FIG. 2. RDI 404further includes at least one connector to receive LR 416. In oneembodiment, LR 416 has the same form factor interface for plugging intoRDI 404 as DART module 408.

In the embodiment shown in FIG. 4A, rather than receiving an analog feedof RF signals, LR 416 receives baseband data from SeRF module 420. Thatis, SeRF module 420 receives the digital RF samples generated by DARTmodule 408 which have been down converted to a sampled baseband digitalsignal. That is, the baseband digital signal provides digital samples ofa DC centered baseband RF signal for the spectrum digitized by DARTmodule 480. SeRF module 420 includes a loop-back feature 430 to providethe sampled baseband digital signal to LR 416. Although FIG. 4A onlyillustrated a single DART module 420, in alternate embodiments, SeRFmodule 420 can loop-back sampled baseband digital signal from any numberof DART modules coupled to SeRF module 420. For example, multiple DARTmodules could be present when a remote unit operates with RF signalstransmitted and received on multiple bands.

In operation, LR 416 evaluates the sampled baseband digital signallooking for a signal from a particular subscriber unit, such as anindividual's cellular phone for example. For example, in one embodiment,LR 416 scans the sampled baseband digital signal to identify anemergency 911 call from a subscriber unit. When LR 416 finds the signalit is looking for, LR 416 generates subscriber unit ranging dataindicating the time at which the signal was received at that remoteunit. LR 416 formats the subscriber unit ranging data for transmissionover an internet protocol (IP) network and outputs the subscriber unitranging data to the SeRF module 420 which in turn routes the subscriberunit ranging data over the Ethernet pipe for transport to a subscriberlocator center such as SLC 140. DART 480 generates a fully downconverted digital representation of the RF band of interest to LR 416.One advantage of having the LR evaluate a sampled baseband digitalsignal rather than an analog RF signal is that the LR does not need tobe designed to perform the digital sampling and down converting of ananalog RF signal itself, which can result in less expensive design andmanufacturing costs for an LR.

In one embodiment, such as FIG. 4A, LR 416 is also coupled to SeRFmodule 420 via an interface 422 that provides bidirectional access tothe Ethernet pipe between remote unit 400 and the host unit. In oneembodiment, interface 422 is a receptacle for a standard 8 Position 8Contact (8P8C) modular plug and category 5/5e cable. In one alternateembodiment, illustrated in FIG. 4B, bidirectional access to the Ethernetpipe between remote unit 400 and the host unit is directly accessible byLR 416 over RDI 424 shown generally at 435. In such an embodiment, SeRFmodule 420 would packet the subscriber unit ranging data using a MACaddress, thus assigning a virtual network port associated with LR 416.

In another alternate embodiment SeRF module 420 receives the digital RFsamples generated by DART module 408, which have been converted intobaseband digital samples. In operation, LR 416 evaluates the basebanddigital samples looking for a signal from a particular subscriber unitas described above. One of ordinary skill in the art upon reading thisspecification would appreciate that DART modules may function tooptionally convert the digital RF samples into intermediate frequency(IF) samples instead of, or in addition to, baseband digital samples.

Instead of generating subscriber unit ranging data at the remote unitsof a distributed antenna system, the same data can be generated at thehost unit. For Example, FIG. 5 is a block diagram illustrating a hostunit (shown generally at 500) of one embodiment of the present inventionsuch as the host unit 102 discussed with respect to FIG. 1. Multipleremote units 506 are coupled to host unit 500, as described with respectto FIG. 1, to form a digital DAS. Host unit 500 includes a host unitdigital to analog radio frequency transceiver (DART) module 508 and ahost unit serial radio frequency (SeRF) module 520. SeRF module 520provides bi-directional conversion between a serial stream of RF datasamples (a SeRF stream) and the multiple high speed optical serial datastreams to and from the remote units 506. Each serial optical datastream includes a digital transport for communicating downlink anduplink transport RF signals as well as an Ethernet pipe between eachremote unit 506 and host unit 500. In the uplink direction, SeRF module520 receives incoming serial optical data streams from a plurality ofremote units and converts each into a serial stream of digitizedbaseband RF data samples, which are summed into a broadband stream of RFdata samples. DART module 508 provides a bidirectional interface betweenSeRF module 520 and one or more base stations, such as BTS 110. As withthe remote units, when host unit 520 operates over multiple bands withmultiple base stations, a separate DART module 508 is provided for eachfrequency band. Host unit 500 also maintains an Ethernet pipe with atleast one base station which provides access to at least one Internetgateway. Location Receiver (LR) 530 is coupled to an Ethernet portinterface 524 of SeRF module 520 via an Ethernet link 525. Ethernet link525 may include a local area network (LAN), wide area network (WAN)having at least one network switch for routing data between interface524 and LR 530. LR 530 is further coupled to SeRF module 520 to receivedigital RF data samples. SeRF module 520 provides LR 530 with access tothe individual serial streams of RF data from remote units 506, beforethe data is summed into the broadband stream of RF data samples.

In operation in one embodiment, LR 530 selects one serial stream of RFdata received from one of the remote units, and listens for a signalfrom a particular subscriber unit, such as an individual's cellularphone for example. LR 530 can observe data from any of the time slots ofany of the bands operating through that remote. For example, in oneembodiment, LR 530 evaluates the RF signal of a particular communicationchannel to make a timing measurement for a particular subscriber unit.When LR 530 finds the signal it is looking for, LR 530 generatessubscriber unit ranging data indicating the time at which the signal wasreceived at that remote unit. Because there is a propagation delaybetween the time an analog RF signal is received at a remote unit 506and the time corresponding digitized RF data samples are received athost unit 500, that delay must be accounted for when generating thesubscriber unit ranging data. LR 530 compensates by determining the timethe digitized RF data samples are received at host unit 500 andsubtracting a propagation delay time associate with that particularremote unit 506. Propagation delay times for each remote unit 506 may beeither known a priori by LR 530 or periodically measured. The subscriberunit ranging data generated by LR 530 thus represents the time the RFsignal was received at the remote unit. LR 530 formats the subscriberunit ranging data for transmission over an internet protocol (IP)network and outputs the subscriber unit ranging data to the SeRF module520 which in turn routes the subscriber unit ranging data over theEthernet pipe for transport to a subscriber locator center such as SLC140. In one embodiment, LR 530 listens for a signal from a particularsubscriber unit simultaneously on multiple serial streams of RF datafrom multiple remote units 506. In that case the subscriber unit rangingdata generated by LR 530 is adjusted for propagation delay based on thewhich remote unit 506 received the corresponding analog RF signal. Inone alternate embodiment, LR 530 comprises several individual locationreceivers each dedicated to observing signals from a specified remoteunit. In one embodiment, LR 530 is remotely configurable, for examplefrom a management interface at a subscriber locator center, to look forspecific samples within a specific RF band received at a specific remoteunit antenna.

Several means are available to implement the systems and methods of thecurrent invention as discussed in this specification. In addition to anymeans discussed above, these means include, but are not limited to,digital computer systems, microprocessors, programmable controllers,field programmable gate arrays (FPGAs) and application-specificintegrated circuits (ASICs). Therefore other embodiments of the presentinvention are program instructions resident on computer readable mediawhich when implemented by such controllers, enable the controllers toimplement embodiments of the present invention. Computer readable mediainclude devices such as any physical form of computer memory, includingbut not limited to punch cards, magnetic disk or tape, any optical datastorage system, flash read only memory (ROM), non-volatile ROM,programmable ROM (PROM), erasable-programmable ROM (E-PROM), randomaccess memory (RAM), or any other form of permanent, semi-permanent, ortemporary memory storage system or device. Program instructions include,but are not limited to computer-executable instructions executed bycomputer system processors and hardware description languages such asVery High Speed Integrated Circuit (VHSIC) Hardware Description Language(VHDL).

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat any arrangement, which is calculated to achieve the same purpose,may be substituted for the specific embodiment shown. This applicationis intended to cover any adaptations or variations of the presentinvention. Therefore, it is manifestly intended that this invention belimited only by the claims and the equivalents thereof. Zone Name:a1,AMD

3. This application is related to U.S. patent application Ser. No.12/555,912, filed on Sep. 9, 2009, filed on even date herewith, entitled“SYSTEMS AND METHODS FOR IP COMMUNICATION OVER A DISTRIBUTED ANTENNASYSTEM TRANSPORT”, attorney docket number 100.1080US01 and which isincorporated herein by reference in its entirety.

1. A method for gathering location data within a geographical area of adigital distributed antenna system, the method comprising: receiving arequest for location services from a subscriber unit located within thegeographical area of the digital distributed antenna system, the digitaldistributed antenna system including a first partition of bandwidth fortransporting digitized radio frequency (RF) signals of one or moremodulated signals, the digital distributed antenna system furtherincluding a second partition of bandwidth for an Ethernet pipe fortransporting Internet Protocol (IP) formatted data; routing the requestfor location services to a subscriber locator center, wherein routingthe request for location services to the subscriber locator centercomprises transporting the request for location services via the firstpartition of bandwidth for transporting digitized RF signals;instructing a plurality of locator receivers within the geographicalarea of the digital distributed antenna system to listen for a signalfrom the subscriber unit; listening for the signal from the subscriberunit at a first locator receiver of the plurality of locator receivers;when the signal is observed by the first locator receiver, recording atime the signal was received and generating subscriber unit rangingdata; and transmitting subscriber unit ranging data back to thesubscriber locator center in an IP formatted message via the Ethernetpipe provided by the digital distributed antenna system.
 2. The methodof claim 1 wherein the first locator receiver is located at a firstremote unit of the digital distributed antenna system.
 3. The method ofclaim 1 wherein the first locator receiver is located at a host unit ofthe digital distributed antenna system.
 4. The method of claim 1 whereinlistening for the signal from the requesting mobile phone at a firstlocator receiver of the locator receivers further comprises: receivingan analog RF signal.
 5. The method of claim 1 further comprising:receiving an analog RF signal; generating a baseband digital signal fromthe analog RF signal; and wherein listening for the signal from thesubscriber unit at the first locator receiver further comprisesprocessing the baseband digital signal to make a timing measurement. 6.The method of claim 1 further comprising: receiving an analog RF signal;generating an intermediate frequency digital signal from the analog RFsignal; and wherein listening for the signal from the subscriber unit atthe first locator receiver further comprises processing the intermediatefrequency digital signal to make a timing measurement.
 7. A remote unitfor a digital distributed antenna system, the remote unit comprising: atleast one digital to analog radio frequency transceiver module forgenerating a digital radio frequency signal from an analog radiofrequency signal received from one or more subscriber units; a locatorreceiver receiving the analog radio frequency signal, the locatorreceiver generating subscriber unit ranging data for a selected firstsubscriber unit of the one or more subscriber units from the analogradio frequency signal, wherein the locator receiver outputs thesubscriber unit ranging data as Internet Protocol (IP) formatted data; aserial radio frequency module coupled to receive the digital radiofrequency signal from the at least one digital to analog radio frequencytransceiver module, the serial radio frequency module further comprisingan interface for receiving the IP formatted data from the locatorreceiver; wherein the serial radio frequency module outputs a serialstream to a host unit, the serial stream comprising a bandwidth with afirst partition for transporting the digital radio frequency signal tothe host unit and a second partition implementing an Ethernet pipe fortransporting the subscriber unit ranging data to the host unit as IPformatted data; and wherein the interface for receiving the IP formatteddata from the locator receiver provides bidirectional access to theEthernet pipe.
 8. The remote unit of claim 7, wherein the locatorreceiver formats the subscriber unit ranging data for routing to asubscriber locator center over an Internet Protocol (IP) network.
 9. Theremote unit of claim 7, wherein the selected first subscriber unit isselected by the locator receiver based on instructions received from asubscriber locator center via the Ethernet pipe.
 10. A remote unit for adigital distributed antenna system, the remote unit comprising: at leastone digital to analog radio frequency transceiver module for generatinga digital radio frequency signal from an analog radio frequency signalreceived from one or more subscriber units; a serial radio frequencymodule coupled to receive the digital radio frequency signal from the atleast one digital to analog radio frequency transceiver module; alocator receiver coupled to the serial radio frequency module andreceiving a loop-back of the digital radio frequency signal from theserial radio frequency module, the locator receiver generatingsubscriber unit ranging data for a selected first subscriber unit of theone or more subscriber units from the digital radio frequency signal,wherein the locator receiver outputs the subscriber unit ranging data tothe serial radio frequency module as Internet Protocol (IP) formatteddata; wherein the serial radio frequency module outputs a serial streamto a host unit, the serial stream comprising a bandwidth with a firstpartition for transporting the digital radio frequency signal to thehost unit and a second partition implementing an Ethernet pipe fortransporting the subscriber unit ranging data to the host unit; andwherein the locator receiver is coupled to the serial radio frequencymodule through an interface that provides bidirectional access to theEthernet pipe.
 11. The remote unit of claim 10, wherein the digitalradio frequency signal is a baseband digital radio frequency signal. 12.The remote unit of claim 10, wherein the digital radio frequency signalis a downconverted intermediate frequency (IF) digital radio frequencysignal.
 13. The remote unit of claim 10, the serial radio frequencymodule further comprising an interface for receiving the IP formatteddata from the locator receiver.
 14. The remote unit of claim 13, whereinthe interface for receiving the IP formatted data from the locatorreceiver comprises an eight-position eight-contact modular plug.
 15. Ahost unit for a digital distributed antenna system, the host unitcomprising: a serial radio frequency module receiving a plurality ofserial streams from a plurality of remote units coupled to the serialradio frequency module, each of the plurality of serial streamstransporting digitized radio frequency samples, each of the plurality ofserial streams comprising a bandwidth with a first partition fortransporting a digital radio frequency signal and a second partitionimplementing an Ethernet pipe for transporting subscriber unit rangingdata to the host unit, wherein the serial radio frequency module sumsthe plurality of serial streams to produce an output to a digital toanalog radio frequency transceiver module for transport to a basetransceiver station; a locator receiver coupled to the serial radiofrequency module and processing digitized radio frequency samples from afirst remote unit of the plurality of remote units to generatesubscriber unit ranging data for a selected subscriber unit incommunication with the first remote unit from the digital radiofrequency signal of a serial stream received from one of the pluralityof remote units, wherein the locator receiver adjust the subscriber unitranging data to compensate for a propagation delay time associated withthe first remote unit; wherein the locator receiver outputs thesubscriber unit ranging data as Internet Protocol (IP) formatted datafor routing to a subscriber locator center; and wherein the locatorreceiver is coupled to the serial radio frequency module through aninterface that provides bidirectional access to the Ethernet pipe. 16.The remote unit of claim 15, wherein the locator receiver outputs thesubscriber unit ranging data to the serial radio frequency module asInternet Protocol (IP) formatted data.
 17. The remote unit of claim 16,wherein the serial radio frequency module outputs the subscriber unitranging data to the base transceiver station via an Ethernet pipe. 18.The remote unit of claim 15, wherein the locator receiver receives adownconverted intermediate frequency (IF) digital radio frequency signalfrom the serial radio frequency module.
 19. The remote unit of claim 15,wherein the locator receiver receives a baseband digital radio frequencysignal from the serial radio frequency module.